蟾蜍在面臨捕食者攻擊時，會出現幾種行為來減低受捕食的風險；把頭貼近地面（head-butting）、蹲伏（crouching）、膨脹身體與分泌毒液等。前兩者可能與腮腺的直接展示有關；後者有欺敵或防止被吞嚥的功能。本研究探討嗜食蟾蜍的擬龜殼花蛇對盤古蟾蜍是否有特殊之捕食行為，檢視成蛇與幼蛇間有無差異，同時檢視是否具備特化器官以捕食蟾蜍；使用紅斑蛇做為盤古蟾蜍毒性作用的實驗對象，瞭解蟾蜍毒是否會對天敵造成影響。在獵物選擇方面，擬龜殼花成蛇喜好捕食體型中等的蟾蜍；幼蛇則傾向捕食小蟾蜍。在攻擊部位與吞食方向的選擇上，成蛇和幼蛇呈現類似的選擇模式。在蟾蜍體型與攻擊部位的選擇上，成蛇由頭部攻擊的多是大的蟾蜍；幼蛇無特殊選擇性，與蟾蜍大小無顯著相關。成蛇吞食蟾蜍的方位（swallowed direction）亦與蟾蜍大小無關; 幼蛇則傾向將較大的蟾蜍由頭部開始吞食，即幼蛇在攻擊後會調整蟾蜍吞食的方位。不論成蛇或幼蛇，吞食一隻蟾蜍所花的時間並無顯著差異，由頭部吞食所花的時間則比從側面或尾部來的短。磨平成蛇的大型上頷齒後，吞食蟾蜍的時間明顯增長，特化的上頷齒可能具備協助進食的功能。蟾蜍遭到攻擊或吞食後，由腮腺分泌毒液的比例並不高；分泌毒液的個體並不會因此而增加蛇吞食的時間。除此之外，在實驗中，蟾蜍面對擬龜殼花時，並無觀察到特殊防禦行為; 因此，擬龜殼花對蟾蜍的捕食行為與一般專食兩生類的陸棲蛇相近。蟾蜍毒是屬於強心配糖體的類毛地黃化合物，具有心臟毒性，蟾蜍毒的毒性強度（LD50），對小白鼠呈現南高北低的差異。分析餵食1 mg/g（毒量/蛇重）蟾蜍毒2小時後的紅斑蛇血液，鈉、鉀、鈣離子濃度均與一般狀態無顯著差異。檢視餵食1、3、10mg/g蟾蜍毒的紅斑蛇心電圖，T波異常、心博過速、心律不整與房室阻滯等症狀均可發現，在高濃度下甚至造成死亡。由此推測，紅斑蛇攝食盤古蟾蜍後會出現蟾蜍毒的中毒反應，因為對毒性的耐受度較高故能捕食蟾蜍。比對嗜食盤古蟾蜍的擬龜殼花、紅斑蛇與台灣赤煉蛇標本，前者並無文獻所言的頸腺構造;擬龜殼花上頷末端的兩枚大型齒可能是為了捕食蟾蜍所特化出的器官。

The behavioral and physiological interaction between Bufo bankorensis and its snake predators, Macropisthodon rudis and Dinodon rufozonatum were investigated in this study. Adult M. rudis preferred medium sized toads but neonate favored to small ones. About seized position of different toad sizes, adult snakes attacked large toads head first but neonates did randomly. On the swallow direction with toad sizes, adult snakes had no preference but neonates swallowed large toads head first, so the neonates could change the direction swallowing preys after preys had been seized. Adult and neonate snakes spent similar time in handling toads with head first ingestion costed less handling time. After the large rear-teeth had been grounded, M. rudis would spend more time in handling preys. In all trials, venom secreted from parotid glands did not seem to prolong handling time on adult snake. After forced fed 1 mg/g toad venom to D. rufozonatum, no significant change of Na+, K+, Ca2+ ion concentrations were observed but significant increasing of heart rates. The ECGs of intoxicated snakes showed typical digitalis-like cardioactive effects as sinus arrhythmia, prolonged P-R interval as varying degrees of atrioventricular block and ventricular fibrillation. The LD50 of the venom of B. bankorensis are different between from toads sampled Northern and Southern Taiwan. In comparison with dissected toad-eating snakes D. rufozonatum, M. rudis and Rhabdophis tigrinus formosanus, I didn’t find any nuchal glands on nuchal-dorsal site of D. rufozonatum and M. rudis.

誌謝 i
摘要 ii
Abstract iii
Contents - 1 -
Introduction - 3 -
Materials and Methods - 8 -
Organisms studied - 8 -
Capture and domestication of animals - 9 -
Food habits of M. rudis - 9 -
Behavioral experiments - 9 -
Prey-handling behavior - 10 -
Function of big rear-teeth - 11 -
Physiological experiments - 11 -
Collection of parotid glands secretion on toads Bufo bankorensis - 11 -
Geographic variation of toad venom - 12 -
Hematology analysis - 12 -
Toad venom tolerance of snakes by EKG analysis - 13 -
Comparative anatomy of specialize tissues and organs - 13 -
Data analysis - 14 -
Results - 15 -
Food habits of M. rudis - 15 -
Behavioral experiments - 15 -
Prey-handling behavior - 15 -
Toad venom secretion with responses of snakes - 16 -
Function of large rear-teeth - 16 -
Physiological experiments - 16 -
Geographic variation of toad venom - 16 -
Hematology analysis - 17 -
Toad venom tolerance of snakes - 17 -
Comparative anatomy of specialize tissues and organs - 18 -
Discussion - 19 -
Food habits of M. rudis - 19 -
The relationship of snake size and toad size - 19 -
Response of toads - 20 -
Toad venom tolerance of snake D. rufozonatum - 21 -
Venom strength of toads - 22 -
Specialized organ on M. rudis - 22 -
Literature Cited - 24 -
Figures and Tables - 30 -
Figure 1 - 30 -
Figure 2 - 31 -
Figure 3 - 31 -
Figure 4 - 32 -
Figure 5 - 33 -
Figure 6 - 34 -
Figure 7 - 35 -
Figure 8 - 35 -
Figure 9 - 36 -
Figure 10 - 37 -
Figure 11 - 38 -
Figure 12 - 38 -
Figure 13 - 39 -
Figure 14 - 39 -
Figure 15 - 40 -
Table 1 - 41 -
Table 2 - 42 -
Table 3 - 43 -
Table 4 - 44 -
Table 5 - 45 -
Table 6 - 45 -
Appendix 1 - 46 -
Appendix 2 - 49 -

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